Stream conditioning for seamless switching of addressable content across transport multiplex, using local stored content as pre-roll and post-roll buffers; in digital television receivers

ABSTRACT

A system, method and apparatus to enable addressable advertising content delivery in which multiple addressable content streams are sent in a transport multiplex, Addressable Content Channel Multiplex, different from the Primary Channel Multiplex on which the Primary Channel is delivered. The Primary Channel is network stream onto which the addressable content is to be inserted. Seamless switch between the Primary Channel and the addressable content streams on the Addressable Content Channel Multiplex is accomplished by using Receiver stored content as interim buffers to which the switching happens prior to switching to a different transport multiplex. These buffers feed the audio and video decoders with content, during the time it takes for the tuner to switch to a different transport multiplex. Pre-roll and Post-roll content buffers are used during switching, one from Primary Channel Multiplex to Addressable Content Channel Multiplex and from Addressable Content Channel Multiplex to Primary Channel Multiplex.

STATEMENT OF RELATED APPLICATIONS

This patent application claims the benefit of and is a divisional ofU.S. patent application Ser. No. 12/629,611 having a filing date of 2Dec. 2009, which claims the benefit of and priority on India PatentApplication No. 3045/CHE/2008 having a filing date of 3 Dec. 2008.

FIELD OF THE INVENTION

This invention relates to digital television transmission systemswherein a minimal buffer is used to store pre-roll and post-roll contentto enable seamless switching across primary and addressable contentchannel multiplexes, while enabling the most efficient use of availablebandwidth.

DISCUSSION OF PRIOR ART

Digital TV systems carry video and audio content as digital compressedstreams over satellite, cable, or IP networks to subscriber homes.Digital TV receivers in subscriber homes uncompress the content andrender on TV sets. Addressable content insertion in digital TV systemsenables, among other applications, a method to provide advertisementstargeted at individual households. For the purpose of this document,“Primary Channel” refers to the currently tuned channel for whichaddressable content streams are to be inserted.

There are multiple methods to accomplish addressable content insertionon digital TV systems. Two macro directions in which this could beaccomplished is by either (i) inserting addressable content on localstorage onto Primary Channel, or (ii) switching to an addressablecontent stream and then switching back to Primary Channel.

To accomplish (i) there is need for local storage space on digital TVreceivers to store complete addressable content. This would need to bestored for multiple ad avails and for multiple TV channels. There is alarge number of installations of digital TV receivers in subscriberhomes that do not have the memory needs to store addressable content intheir local storage. This is a big deterrent for implementing thisapproach for existing subscriber homes.

Switching to an addressable content stream and then switching back toPrimary Channel is an option suitable for existing digital TV receiverin subscriber homes, as it does not assume the need for local storage onthe receivers. This is the approach taken by SCTE (Society of CableTelecommunications Engineers), which is an organization that has come upwith a standard that provides a form of addressable content delivery ondigital TV systems. Per SCTE standards, conditioning the video and audiostreams at the head-end enables switching between the Primary Channeland the addressable content stream and vice-versa. This standard iscalled SCTE DVS-766.

In order to adhere to this standard, multiple advertisement streams aresimultaneously delivered to digital TV receivers. The receiver selectsone of the addressable content streams based on received addressinginformation and locally stored selection criteria, and switches at theappropriate time.

The DVS-766 standard defined two stream conditioning systems, Level-0(L0) which accomplishes non-seamless switching and Level-1 (L1) thataccomplishes seamless switching.

Level-0 systems described in FIG. 1, permit addressable content streamsdesignated for insertion onto the Primary Channel, to be transmitted ina transport multiplex different from the one that is carrying thePrimary Channel. The Receiver tunes to the RF channel carrying theAddressable Content Channel multiplex that contains the addressablecontent streams and then selects and decodes the required addressablecontent stream.

In this system, addressable ads are carried on either the same ordistinct multiplexes than the ones carrying the network feed. 11 is thefirst multiplex carrying the network feed along with a generic ad 13that is also carried in the same multiplex, which would require noswitching between multiplexes. Alternatively, the addressable ad 14could inhabit its own multiplex 12, which would require a channel switchand potentially introduce a latency.

Level-0 switching is non-seamless because of the need to have fillerduring the time the tuner takes to switch to a different multiplex, asshown in FIG. 2. There now exist two channels, 20 and 21. During thesefillers black frames and silent audio data are transmitted on themultiplex so as to avoid displaying any artifacts or losing anysignificant audio and video data.

Bandwidth for the addressable content streams in a single transportmultiplex used as a shared resource for all addressable contentinsertions across all needed TV channels in the transmission system, isan optimal way of planning transmission bandwidth. But L0 comes with anon-seamless switching when addressable content is inserted.

In Level-1 systems described in FIG. 3, all the addressable contentstreams for a particular Primary Channel are present in the sametransport multiplex as that of the Primary Channel. The addressablecontent streams are conditioned to enable receivers to switch to theselected addressable content seamlessly.

Level-1 systems provide a seamless switch mechanism, but are hard toimplement from a cable transmission bandwidth planning perspective.Bandwidth needs to be allocated in every multiplex that contains TVchannel which needs addressable content insertion support. In cablesystems there are multiple 6 MHz transport multiplexes in each of whichbandwidth needs to be allocated for the simultaneous addressable contentstreams. In satellite systems, the cost of RF spectrum is prohibitive tosupport bandwidth allocation for multiple addressable content streamsacross different transport multiplexes.

In summary L0 and L1 are different compromises between viewingexperience and flexibility in transmission bandwidth, given theassumption that there is no local storage to store addressable contentfor local insertion, on the receiver.

SUMMARY OF THE INVENTION

In this invention a system is described that provides seamless switchingacross Primary Channel and the addressable content streams, yet havingthe addressable content streams sent over a different transportmultiplex from that of the Primary Channel. The system assumes thatthere is temporary local storage to store a small duration of Pre-rolland Post-roll content sets. These content sets are used as buffercontent that are decoded and presented to user during the time the tunertakes to tune to a different transport multiplex.

This invention thus provides a method to provide seamless switchingacross streams on digital television receivers and set-top boxes, with aprimary content stream and one or more addressable content streams beingsent over different transport multiplexes such as primary transportmultiplex and addressable content transport multiplex while optimizingbandwidth allocated in a digital television network and using thestorage available on digital television receivers and set-top boxescomprising the steps of:

-   -   a. Switching from the primary content stream to an addressable        content stream further comprising the steps of:        -   i. Switching to a locally stored pre-roll content to be            rendered, upon receiving a signal switch point, in the            primary content stream;        -   ii. Tuning to the addressable content transport multiplex,            in parallel to the pre-roll content rendering;        -   iii. Switching to the addressable content stream on the            currently chosen multiplex at a pre-determined decision            point after the completion of tuning; and    -   b. Switching back from the addressable content stream to the        primary content stream, further comprising the steps of:        -   i. Switching to a locally stored post-roll content that is            rendered;        -   ii. Tuning to the primary transport multiplex, in parallel            with post-roll content rendering; and    -   c. Switching to the currently tuned multiplex at a        pre-determined decision point after the completion of tuning.

This invention also provides an apparatus to provide seamless switchingacross streams on digital television receivers and set-top boxes, with aprimary content stream and one or more addressable content streams beingsent over different transport multiplexes such as primary transportmultiplex and addressable content transport multiplex while optimizingbandwidth allocated in a digital television network and using thestorage available on digital television receivers and set-top boxescomprising a head end architecture and a receiver architecturecharacterized by an enhanced ad-server, an enhanced splicer to performthe steps of:

-   -   a. Switching from the primary content stream to an addressable        content stream further comprising the steps of:        -   i. Switching to a locally stored pre-roll content to be            rendered, upon receiving a signal switch point, in the            primary content stream;        -   ii. Tuning to the addressable content transport multiplex,            in parallel to the pre-roll content rendering;        -   iii. Switching to the addressable content stream on the            currently chosen multiplex at a pre-determined decision            point after the completion of tuning; and    -   b. Switching back from the addressable content stream to the        primary content stream, further comprising the steps of:        -   i. Switching to a locally stored post-roll content that is            rendered;        -   ii. Tuning to the primary transport multiplex, in parallel            with post-roll content rendering; and    -   c. Switching to the currently tuned multiplex at a        pre-determined decision point after the completion of tuning.

In a preferred embodiment there is provided an apparatus to provideseamless switching across streams on digital television receivers andset-top boxes, with a primary content stream and one or more addressablecontent streams being sent over different transport multiplexes such asprimary transport multiplex and addressable content transport multiplexwhile optimizing bandwidth allocated in a digital television network andusing the storage available on digital television receivers and set-topboxes comprising a head end architecture and a receiver architecturewhere:

-   -   a. The head end architecture further comprises:        -   i. A vendor-specific content preparation system;        -   ii. An enhanced ad server;        -   iii. A vendor-specific server;        -   iv. An enhanced splicer;        -   v. An in-band channel modulator;        -   vi. An ad-channel modulator;        -   vii. An out of band channel modulator; and        -   viii. A signal combiner;    -   b. The receiver architecture further comprises:        -   i. A tuner;        -   ii. One or more transport demultiplexers, that demultiplex            the transport stream coming from the tuner and transmits            streams to one or more decoders;        -   iii. A decision engine which instructs a switch engine and            one or more pre-roll and post-roll content server based on            selection criteria meta-data;        -   iv. A switching engine which controls the tuner and program            ID filters (or MD filters) on the transport demultiplexers            to enable seamless switching between multiplexes and stored            content streams to be passed onto the decoders;        -   v. A pre-roll and post-roll content server that accesses one            or more data-stores containing this content and streams them            to the Transport Demultiplexer as stored content streams;        -   vi. A trigger signal decoder used to decode signals that may            be on a separate data-stream filtered to it;        -   vii. A video decoder;        -   viii. An audio decoder; and        -   ix. A data-store for pre-roll and post-roll content.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 describes the Level-0 systems;

FIG. 2 shows how Level-0 switching is non-seamless because of the needto have filler during the time the tuner takes to switch to a differentmultiplex;

FIG. 3 shows Level-1;

FIG. 4 shows the stream conditioning system of the present inventiontermed as Splice'nSwitch;

FIG. 5 depicts an example with Pre-roll and Post-roll Content Sets andtwo transport multiplexes for the present invention;

FIG. 6 shows an example of head-end architecture that suitable for aSplice'nSwitch system;

FIG. 7 shows an example Receiver supporting Splice'nSwitch capability;

FIGS. 8 and 9, describes one embodiment of the method for implementingthe Switching engine; and

FIG. 10 shows the Splice'nSwitch-system message sequence chart.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In this invention, a system that provides seamless switching acrossPrimary Channel and the addressable content streams, while having theaddressable content streams sent over a different transport multiplexfrom that of the Primary Channel, is described. The system assumes thatthere is temporary local storage on the receiver to store a smallduration of Pre-roll and Post-roll content sets. These content sets areused as buffers and are decoded and presented to viewers during the timethe tuner takes to tune to a different transport multiplex.

It is seen that in existing digital TV receivers in subscriber homesthere is free RAM (volatile memory) that is available to store thePre-roll and Post-roll content sets. This invention does not presume thetype of local storage on the digital TV receiver, and only assumes thatthere is an existence of minimal local storage to allow for storingcontent that is rendered during the tuner switch latency.

Stream Conditioning

The stream conditioning system described in this invention termed asSplice'nSwitch. FIG. 4, describes the concept as sequence of activitiesin a digital TV receiver. The Primary Channel Multiplex 401 is thechannel on which the currently tuned television content is playing. Thisprimary channel also contains advertisements that are part of thetelevision channel 403 a, 403 b, and 403 c referred to as national ads,in this document. These are default advertisements which appear on thePrimary Channel Multiplex and are not consumer-oriented orcustomer-specific. The Addressable Content Channel Multiplex 402 has anumber of addressable content streams 404 a, 404 b, that are created byindividual vendors, based on customer demographics. For purposes of theexample discussed in this figure, the primary channel multiplex 401 hasa television channel “p” 405 playing, when a local ad-avail 405 a isscheduled to appear. While this ad avail 405 a could be the defaultnational advertisement 403 a, 403 b, 403 c, this invention discusses theswitching mechanism to an addressable content channel multiplex 402 thatserves up addressable content streams. An event, called the SignalSwitch Point 406 occurs on the primary channel multiplex, when an adavail is set to begin. Once this event triggers, the system switches toa pre-roll content 407 buffer, which is typically stored locally on adigital television receiver (also called a set-top box, in some cases).Simultaneous to this transition to the pre-roll content 407 buffer, thetuner 408 tunes into the addressable channel multiplexer 408 a. On alogical decision point, which is typically after the tuning duration hastranspired, the system switches 409 to the addressable content feed 404b on the currently tuned channel multiplexer. When the addressableadvertisement ends, the system reaches a Signal Switch Point 410 on theaddressable content channel multiplex. The system switches to apost-roll content buffer 411, which is also on the television receiver.In parallel to this event, the tuner 408 tunes back 408 b to the PrimaryChannel Multiplex. On a logical decision point, which is typically afterthe tuning duration has transpired, the system switches 413 back to theprimary channel 414 on the currently tuned channel multiplexer.

FIG. 5 depicts a more detailed example with Pre-roll and Post-rollContent Sets and two transport multiplexes 501 and 502 which serve thecontent to be shown to the viewers during an avail 503. The transportmultiplexes each showing the presence of a Splice'nSwitch system with aPrimary channel containing content on the primary channel 501 a and themetadata trigger signals 501 b. A default ad with video and audiostreams associated with it 501 d, 501 e also exists on the primarychannel. In this example, the addressable Content Set is comprised oftwo addressable content streams 502 a, 502 b with respective video 502d, 502 f and audio 502 e, 502 g components, and also has metadatatrigger signals 502 c. The metadata trigger signals 501 h, 502 j are notmandatory and work in conjunction with the Signal Switch Points 501 c,502 i on each of the Primary Channel and Addressable Content Channelmultiplexes, respectively. Besides trigger information, the metadata 501i, 502 h could further contain additional information for the Decisionengine. Time boundaries are specified within which the transport packetscontaining video, audio and data associated with Addressable Content Setmay be transmitted in the Addressable Content Channel Multiplex.

It is shown that there are two each of Pre-roll 503 a, 503 b andPost-roll 503 c, 503 d content that relate to each of the correspondingaddressable content on the Addressable Channel Multiplex. Although twodifferent Pre-roll and Post-roll Content Sets are shown here, theinvention makes no assumptions on the number of Pre-roll and Post-rollContent Sets and their specific mapping to the streams in theAddressable Content Set.

One of the addressable content designated as default, with correspondingaudio and video components 501 d, 501 e is present in the PrimaryChannel. This exists in the same PIDs as the Network's video and audioPIDs 501 f, 501 g. This default addressable ad content is updated withthe corresponding Pre-roll and Post-roll content on the head-end. Thisdefault ad content will be selected by Receivers that do not implementSplice'nSwitch mechanism and by Splice'nSwitch enabled Receivers that donot respond to selection criteria for this Addressable Content Set. Theremaining addressable content streams are present in the AddressableContent Channel Multiplex 502 d, 502 e, 502 f, 502 g.

An opportunity to switch from the Primary Channel video and audiostreams is shown as a Signaled Switch Point 501 c. Another SignaledSwitch Point 502 i on the Addressable Content Channel Multiplex marksthe opportunity to switch back to the Primary Channel stream. Pre-rolland Post-roll content buffers 503 a, 503 b, 503 c, 503 d exist on thelocal storage from which the decoder starts rendering just after thecorresponding Signaled Switch Point 501 c, 502 i. During this time theReceiver tunes to new multiplex and acquires the new channel to decode.Once the local stored content rendering is complete, it switches todecoding content from the new channel, to which the Receiver has tunedto.

The duration of the Pre-roll and Post-roll content is greater than thetime required for the slowest Receiver to tune to and begin decoding thenew multiplex.

Pre-roll and Post-roll content needed for this method is expected to beavailable locally on the digital TV receiver. This invention does notmake any assumptions relating to following aspects of the Pre-roll andPost-roll content,

-   -   a) Bitrate or any other decoding properties    -   b) Origin of the content (could be one of and not limited to        being locally generated or sent over the transmission).    -   c) Time when the content has reached local storage, if sent from        an external source    -   d) Length of the content and the rendering duration, with the        only constraint that the content render time is greater than or        equal to the maximum time the tuner takes to switch from one        multiplexer to another.    -   e) Rules or decisions that determine the specific content to        render during a switch activity, given there could be multiple        content for each of Pre-roll and Post-roll

Pre-roll and Post-roll content could be as simple as a single staticslide to being the first and last parts of the corresponding addressablecontent sent on the addressable content stream.

Although this invention does not assume anything related to the sourceof the Pre-roll and Post-roll content, for completeness of understandingfew possible mechanisms are discussed.

In one possible method, the Pre-roll and Post-roll content could be sentby the head-end on all the multiplexes on a periodic basis, to be storedon the Receiver. Each of the Receiver shall identify if the Pre-roll andPost-roll content is addressed to the addressable group to which theReceiver belongs, and then stores the corresponding Pre-roll andPost-roll content. This method is suitable for sending static slide orPre-roll, Post-roll content that are distinct from that of theaddressable content stream.

In another possible method, assuming Pre-roll and Post-roll content arefirst and last parts respectively of the addressable content stream,then this content could be sent on the multiplex prior to the arrival ofthe Signaled Switch Point, such that the content needed for renderingjust after the Signaled Switch Point is available for the decoder. Thisinvention does not mandate any content constraints on the Pre-roll andPost-roll.

Timing

The transmission of addressable content stream on the AddressableContent Channel Multiplex is typically aligned in time to:

(Signaled Switch Paint on the Primary Channel Multiplex+CorrespondingPre-Roll Content Duration).

For ease of implementation it is recommended that all Pre-roll contentin a Pre-roll Content Set are of the same duration although thisinvention does not preclude varying Pre-roll content durations. Thetransmission of the Primary Channel on the Primary Channel Multiplex isaligned in time with the end of avail duration. The default addressablead content that is sent as part of the Primary Channel is aligned intime with the Signaled Switch Point on the Primary Channel Multiplex,and is expected to last the complete avail duration.

Signaled Switch Point on the Addressable Channel Multiplex is aligned intime to,

(End of Avail Duration—Corresponding Post-Roll Content Duration).

For ease of implementation it is recommended that all Post-roll contentin a Post-roll Content Set are of the same duration although thisinvention does not preclude varying Post-roll content durations.

In scenarios with varying Pre-roll and Post-roll content for each of theaddressable content streams, each of the addressable content streamsduration and their transmission times would be different. Thepreparation of the addressable content streams that fall within theavail boundaries is expected to done by the head-end.

Trigger Signals 501 h, 502 j are associated with each Signaled SwitchPoint to indicate the location of the Switched Point in time. TheTrigger Signal data could be any of data method inside the multiplex,including and not limited to data in the video and audio streams. In theAddressable Content Channel Multiplex, it is possible to have multipleTrigger Signals to signal different Signaled Switch Points for differentaddressable content streams. One possible Trigger Signal could be atransport packet using a unique PID containing system clock value onwhen to switch. There could also be two separate Trigger Signals, oneeach for video and audio streams.

Signaled Switch Points shall occur only when both the video and audiodata needed for rendering, prior to switching, has been received.Signaled Switch Point and the associated Trigger Signal could beReceiver generated events and do not mandate the need for a data elementon the transport stream. The Signaled Switch Point could be an eventbased on a pre-fetched avail schedule available on the Receiver. In suchcases of Receiver generated Signaled Switch Point, it is possible thatthere is no corresponding Trigger Signal.

The primary essence of this invention is the mechanism to make aseamless switch when switching across multiplexes, by using a Pre-rolland Post-roll pre-stored content to fill the time the tuner takes totune to the needed multiplexer. Those skilled in this art shall be ableto extend this concept and would appreciate that all of those extensionsthat come under the purview of this invention.

Splice'nSwitch System

FIG. 6, shows an example of the system architecture of the presentinvention. A vendor-specific content-preparation system 601 acceptsaddressable content 601 a and selection criteria 601 b and handles theconditioning of the addressable content streams. It also handles thepreparation and conditioning of Pre-roll and Post-roll contentcorresponding to different addressable content streams. Some parts ofthe conditioning could also be handled by the Splicer 604. Thevendor-specific content preparation system processes the incomingaddressable content 601 a and selection criteria 601 b to createaddressable content streams 601 c and pre-roll and post-roll content 601d. This is fed separately to the ad server 602 and the vendor-specificserver 603.

The Splice'nSwitch enhanced Ad server 602 sends the needed addressablecontent streams to the Splicer 604. The Ad server streams the neededaddressable content streams at the chosen time to the Splicer to insertinto the Multiplex for transmission to the Receivers.

The Vendor specific Pre-roll, Post-roll content and metadata server 603handles the transmission of metadata including but not limited to dataneeded for switching and Pre-roll, Post-roll content decision making onthe Receiver. This server also shall send the needed Pre-roll andPost-roll content to the Receivers. The policy for content insertion,and the exact mechanics and type of content sent for Pre-roll, Post-rollinsertions on the Receiver is vendor-specific and is outside the scopeof this invention.

The Splicer 604 handles the insertion of Addressable Content Sets 602 a,602 b, 602 c and Trigger Signals 602 d onto the selected multiplex. Theprimary channel content along with trigger data 604 a is sent to anin-band channel modulator 605. The addressable content along withtrigger data 604 b is sent to an ad channel modulator 606. These areused in conjunction with the output on an out of band (OOB) channelmodulator 607 and communicated to the receiver 608. The Vendor specificcontent preparation system communicates the decision engineconfigurations to the Decision engine on the Receiver through the OOBchannel.

It is expected that all of the Primary Channel stream, AddressableContent Set and the Pre-roll, Post-roll Content Set are conditioned soas to insure that there are no video and audio artifacts produced on theReceiver, when a switch happens between them. As an illustration, forMPEG-2 content insertion SMPTE-312M standard specifies the list ofcriteria for conditioning the streams so as ease seamless switching onthe Receiver.

Trigger Signals 604 a need to be inserted onto the Primary ChannelMultiplex and the Addressable Content Channel Multiplex 604 b fordefining the Switched Signal Points. This is taking into account thePre-roll and Post-roll content duration for each of the addressablecontent streams.

It is possible under the scope of this invention that the AddressableContent Multiplex is used to send other network streams in addition tothe Addressable Content Set. This is a possibility in Satellite TVscenarios where multiplex bandwidth is large and spectrum limitationswould not afford allocating exclusive multiplex for the AddressableContent Set.

The Splice'nSwitch enhanced Ad server 602, Vendor specific Pre-roll,Post-roll content and metadata server 603 and Vendor-specific contentpreparation system 601 could reside outside the physical head-endpremises and connected over a network to the head-end infrastructure.This invention in no way dictates the physical availability of thesecomponents in a head-end.

Splice'nSwitch Receiver

FIG. 7 shows a detailed example of a Receiver of the present invention,which supports Splice'nSwitch requirements. The Transport demultiplexer701 demultiplexes the transport stream coming from the tuner and passesthe video to the video decoder 702 and audio to the audio decoder 703.It is assumed for this example that the Trigger Signal is on a separatedata stream and that is filtered to a Trigger Signal decoder 704. TheTrigger Signal is expected to be available early enough so as to providesufficient time for the switching engine to take its decision and do theswitching. The Switching engine 705 gets the needed switch instructionfrom the Decision engine 706. Switching engine controls the tuner 707and the PID filters on the Transport demultiplexer to make seamlessswitch between multiplexes and stored content streams to be passed ontothe decoders. The video and audio decoders are unaware of the switch. Asnetwork streams and the Pre-roll, Post-roll content are conditioned, bycontrolling the Tuner and the Pre-roll, Post-roll content server, theSwitching engine can make a seamless switch.

The Decision engine 706 in addition to instructing the switch engine,also instructs the Pre-roll and Post-roll content server on the specificPre-roll, Post-roll content to be served on each of the avails, based onthe selection criteria metadata 708 received from the head-end. Theselection criteria and the operation of the Decision engine are outsidethe scope of this invention. It is assumed for this example that thePre-roll and Post-roll content are available on a separate data streamthat is stored onto a Pre-roll, Post-roll content store 709 on theReceiver. The Pre-roll, Post-roll content server 710 accesses thisstore, on instructions from the Decision engine and streams them ontothe transport multiplex, as timed by the Switching engine.

FIGS. 8 and 9, describes one embodiment of the method for implementingthe Switching engine. This should not be construed as the only way toimplement the Switching engine.

On Trigger Signal 801 on the Primary Channel, the Switching enginecoordinates with the Decision engine to identify the Pre-roll, Post-rollcontent and the addressable content stream 802 to which the switchingneeds to happen.

On the Signaled Switch Point 803, two activities are donesimultaneously.

-   -   (i) The Transport demultiplexer PID filters are set to access        streams from Pre-roll, Post-roll content server 804. And then        the Pre-roll, Post-roll content server is instructed to stream        the identified pre-roll content to be rendered by the decoders        805.    -   (ii) The tuner is instructed to tune to the Addressable Content        Channel Multiplex. 806

Once both (i) and (ii) activities are complete 807, then the Switchingengine sets the Transport demultiplexer PID filters to access streams onthe selected addressable content stream 808.

On the Addressable Content Channel Multiplex, once the Signaled SwitchPoint 901 is reached, two activities are done simultaneously,

-   -   (i) The Transport demultiplexer PID filters are set to access        streams from Pre-roll, Post-roll content server 902. And then        the Pre-roll, Post-roll content server is instructed to stream        the identified post-roll content to be rendered by the decoders        903.    -   (ii) The Tuner is instructed to tune to the Primary Channel        Multiplex 904.

Once both (i) and (ii) are complete 905, then the Switching engine setsthe Transport demultiplexer PID filters to access the Primary Channel906.

This would complete one Splice'nSwitch activity for a given avail. It isassumed that the Switching engine handles latency needs for setting theTransport demultiplexer PID filters and for addressable content decisionmaking, by controlling the rate of content streaming from the localPre-roll, Post-roll content server. It is expected that there are noartifacts in audio and video are introduced during the switch process.

FIG. 10 shows the overall system and messages between various componentsof the one embodiment of the system. The components of the Receiver 200including Switching engine 201, Pre-roll, post-roll content server 202,Decision engine 203, Transport multiplexer 204 and the Tuner 205 areshown on the right hand side. The components outside the Receiver 100including the Vendor-specific content preparation system 101, the Adserver with splice'nswitch enhancements 102, the Vendor-specificPre-roll, Post-roll content and metadata server 103, the Splicer withsplice'nswitch enhancements 104 and the OOB 105 are shown on the lefthand side. The messages across components are explained below:

Decision engine configurations 101 a are sent by the Vendor specificcontent preparation system 101 to the OOB channel 105. This is expectedto be multicast over all the multiplexes so as to be received by as manyof the Receivers. The specific policy and frequency of sending theDecision engine configuration is implementation dependent and is outsidethe scope of this invention. The OOB channel is used to send theconfiguration information to the Decision engine on the Receiver 105 b.

Pre-roll and post-roll content that needs to be sent to the Receiver areprepared by the Vendor-specific content preparation system 101 b. Basedon the implementation policy the Vendor specific server (Pre-roll,Post-roll, metadata streamer) 103 a implementing the policy shall sendthe specific Pre-roll, Post-roll content to the Pre-roll, Post-rollcontent server on the Receivers. The specific timeframe and frequencyfor sending Pre-roll, Post-roll content is implementation dependent andis outside the scope of this invention.

On receiving the SCTE 35 marker 104 e on the Primary Channel, theSplicer 104 requests the Vendor-specific server for the specificswitching and Pre-roll, Post-roll selection metadata to be sent to theSwitching engine on the Receivers. The response to this is sent by theVendor-specific server 103 e.

Trigger is generated by the Vendor-specific server in response to theSCTE 35 marker on the Primary Channel. The Trigger message is sent tothe Splicer 103 c and an intimation of this signal is sent both to theAd server 103 d and the Vendor-specific content preparation system 102a. On receiving the Trigger signal from the Vendor-specific server, theSplicer sends the Trigger 104 f with the pre-roll time to the Switchingengine on the Receiver over the Primary Multiplex, along with theselection decision. The Trigger intimates the upcoming Signaled SwitchPoint after the pre-roll time for the Receiver to switch at that timeinstant.

On reception of Trigger intimation, the Vendor-specific contentpreparation system prepares both the Default addressable content 101 dand the Addressable Content Set 101 e and sends it to the Ad server. Atthe end of pre-roll duration after the trigger, at the time thatcoincides with the Signaled Switch Point on the Primary Multiplex on theReceiver, the Ad server streams the Default addressable content 102 b tothe Splicer. The Splicer splices this content onto the Primary Channelin lieu of the Network content and sends that as the Primary Channel onthe Primary Multiplex 104 a.

On reception of the Trigger, the Switching engine on the Receiverprepares for the arrival of the Signaled Switch Point after the pre-rollduration by communicating the decision for switch with the Decisionengine. At the Signaled Switch Point instant, the Switching engineinstructs the following, (i) Pre-roll, Post-roll content to stream thecorresponding Pre-roll content 201 a, (ii) Transport Multiplexer toswitch to the Pre-roll, Post-roll content server stream instead of theNetwork streams (in the case of the default Primary Channel not meetingthe addressability needs on that Receiver) 201 b and (iii) Tuner to tuneto the Addressable Content Channel Multiplex 201 c.

At the end of time elapsed which is Signaled Switch Point+the Pre-rollcontent duration for the corresponding addressable content stream, theAd server sends the addressable content streams to the Splicer 101 e tobe sent to the Receiver 104 b. For the sake of this embodiment, it isshown that all of the Addressable Content Set has Pre-roll and Post-rollcontent of the same duration and hence it is shown that the Ad serverand subsequently the Splicer sends the complete Addressable Content Setto the Receiver at the same time instant. The invention does notpreclude conditions where there are different Pre-roll, Post-rollcontent durations for each of the addressable content streams and thusthe Ad server would stream each of the addressable content streams atdifferent points of time to synchronize with the completion of thePre-roll content duration on the corresponding Receivers consumingspecific addressable content streams.

At the end of the Pre-roll content rendering duration on the Receiver,the Switching engine instructs the Transport Demultiplexer to switch tothe Addressable Content Channel Multiplex 201 d (if the addressabilityon the Receiver is not the Default Primary Channel content). When thisswitch happens, the decoder on the Receiver shall start rendering thecorresponding addressable content stream that has been streamed from theheadend.

The stream duration of the addressable content stream that is determinedby the Avail duration−(Pre-roll content duration+Post-roll contentduration), for each of the addressable content streams. The Ad serverdetermines and controls the stream duration of the content sent by theSplicer.

There is a Signaled Switch Point to switch back from the AddressableContent Channel Multiplex to a Post-roll content. There could be anoptional Trigger sent from the headend, where the Vendor-specific servershall send the Trigger information 103 f to the Splicer to be sent overthe Addressable Content Channel Multiplex to the Receivers 104 d.

At the completion of the stream duration, the Switching engine on theReceiver instructs the following, (i) Pre-roll, Post-roll content serverto stream the corresponding Post-roll content 201 e, (ii) TransportDemultiplexer to switch from the Addressable Content Channel Multiplexto the Pre-roll, Post-roll content stream 201 f, and (iii) Tuner to tuneto Primary Multiplex 201 g.

On completion of the Avail duration, at the headend, the Splicerswitches the Primary Channel on the Primary Multiplex back to theNetwork stream 104 c.

The completion of the Avail duration, the Receiver completes therendering of the Post-roll content and that time instant, the Switchingengine on the Receiver instructs the Transport Demultiplexer to switchto the Primary Channel Multiplex 201 h.

This sequence completes one Splice'nSwitch activity interaction betweenthe headend and the corresponding Receivers.

The invention claimed is:
 1. An apparatus to provide seamless switchingacross streams on digital television receivers and set-top boxes, with aprimary content stream and one or more addressable content streams beingsent over different transport multiplexes such as primary transportmultiplex and addressable content transport multiplex while optimizingbandwidth allocated in a digital television network and using thestorage available on digital television receivers and set-top boxescomprising a head end architecture and a receiver architecture where: a.The head end architecture further comprises: i. A vendor-specificcontent preparation system; ii. An enhanced ad server; iii. Avendor-specific server; iv. An enhanced splicer; v. An in-band channelmodulator; vi. An ad-channel modulator; vii. An out of band channelmodulator; and viii. A signal combiner; b. The receiver architecturefurther comprises: i. A tuner; ii. One or more transport demultiplexers,that demultiplex the transport stream coming from the tuner andtransmits streams to one or more decoders; iii. A decision engine whichinstructs a switching engine and one or more pre-roll and post-rollcontent server based on selection criteria meta-data; iv. The switchingengine which controls the tuner and program ID filters (or PID filters)on the transport demultiplexers to enable seamless switching betweenmultiplexes and stored content streams to be passed onto the decoders;v. The pre-roll and post-roll content server that accesses one or moredata-stores containing this content and streams them to the TransportDemultiplexer as stored content streams; vi. A trigger signal decoderused to decode signals that may be on a separate data-stream filtered toit; vii. A video decoder; viii. An audio decoder; and ix. A data-storefor pre-roll and post-roll content.
 2. The apparatus of claim 1 wherethe vendor-specific content preparation system: a. Sends the decisionengine configuration to be multicast over multiplexes to the out of bandchannel modulator; b. Sends the pre-roll and post-roll content to thevendor-specific server; c. Sends the selection criteria to thevendor-specific server; d. Sends a default addressable content to theenhanced ad server; and e. Sends the addressable content set to theenhanced ad server.
 3. The apparatus of claim 1 wherein the enhanced adserver: a. Receives trigger intimation from the vendor specific server;b. Sends the default addressable content for splicing on the primarychannel to the enhanced splicer; and c. Sends the addressable contentset to the enhanced splicer.
 4. The apparatus of claim 1 wherein thevendor-specific server: a. Sends pre-roll and post-roll contenttransmitted based on vendor-specific policy to the pre-roll, post-rollcontent server; b. Receives metadata requests of the decision enginefrom the enhanced splicer; and c. Sends one or more triggers to theenhanced splicer.
 5. The apparatus of claim 1 wherein the enhancedsplicer: a. Sends decision engine meta-data requests to thevendor-specific server; b. Sends triggers intimating upcoming signaledswitch point with selection decision on the primary transport multiplexto the switching engine; c. Sends primary stream data spliced withdefault addressable content stream sent on the primary transportmultiplex to the transport demultiplexer; d. Sends addressable contentset streamed on addressable content transport multiplex to the transportdemultiplexer, as and when the content is provided by the enhanced adserver; e. Sends optional trigger intimating upcoming signaled switchpoint sent on addressable content channel multiplex to the switchingengine; and f. Sends primary channel switched to network stream onprimary transport multiplex to the transport demultiplexer upon thecompletion of an avail duration.
 6. The apparatus of claim 1 wherein thead channel modulator modulates ad content streams onto the pre-allocatedaddressable content transport multiplex.
 7. The apparatus of claim 1wherein the out of band channel modulator sends the decision engineconfiguration to the decision engine.
 8. The apparatus of claim 1wherein the signal combiner combines modulated signals from alltransport multiplexes and sends over a transmission link.
 9. Theapparatus of claim 1 wherein the tuner: a. Receives a message from theswitching engine asking it to tune to the addressable content transportmultiplex; and b. Receives a message from the switching engine to tuneto the primary transport multiplex.
 10. The apparatus of claim 1 whereinthe transport demultiplexers: a. Demultiplex the transport stream comingfrom the tuner and passes the video and audio streams to the respectivedecoders; b. Receive a message from the switching engine to switch topre-roll and post-roll content; c. Receive a message from the switchingengine to switch to the addressable content transport multiplex; d.Receive a message from the switching engine to switch to pre-roll andpost-roll content server; and e. Receive a message from the switchingengine to switch to the primary transport multiplex.
 11. The apparatusof claim 1 wherein the decision engine: a. Instructs the switchingengine; and b. Instructs the pre-roll and post-roll content server onthe specific content to be rendered on each of the instances based onthe selection criteria.
 12. The apparatus of claim 1 wherein thepre-roll and post-roll content servers receive from the switching engineto stream content.
 13. The apparatus of claim 1 wherein the switchingengine: a. Sends a message to the tuner to tune to the addressablecontent transport multiplex; b. Sends a message to the pre-roll andpost-roll content servers to stream content; c. Sends a message to thetransport demultiplexer to switch to pre-roll and post-roll content; d.Sends a message to the transport demultiplexer to switch to theaddressable content transport multiplex; e. Sends a message to thetransport demultiplexer to switch to pre-roll and post-roll contentserver; and f. Sends a message to the transport demultiplexer to switchto the primary transport multiplex.
 14. The apparatus of claim 1 whereinthe switching engine, upon receiving a trigger signal on the primarystream, co-ordinates with the decision engine to identify the pre-roll,post-roll and addressable content streams to switch to such that on thesignaled switch point, two activities are executed simultaneously: a)The transport demultiplexer PID filters are set to access streams frompre-roll, post-roll content servers, which in turn is instructed tostream the pre-roll content to be rendered by the decoders; and b) Thetuner is instructed to tune to the addressable content transportmultiplex following the completion of which, the switching engine setsthe transport demultiplexer PID filters to access content on theselected addressable content stream.
 15. The apparatus of claim 1wherein the switching engine, upon receiving a trigger signal on theaddressable content stream, co-ordinates with the decision engine toidentify the pre-roll, post-roll and primary stream to switch to suchthat on the signaled switch point, two activities are executedsimultaneously: a) The transport demultiplexer PID filters are set toaccess streams from pre-roll, post-roll content servers, which in turnis instructed to stream the post-roll content to be rendered by thedecoders; and b) The tuner is instructed to tune to the primarytransport multiplex following the completion of which, the switchingengine sets the transport demultiplexer PID filters to access content onthe primary stream.